5 messages in org.r-project.r-helpRe: [R] subsetting dataframe by rowna...| From | Sent On | Attachments |
|---|---|---|
| Alexy Khrabrov | Oct 11, 2008 8:57 pm | |
| Prof Brian Ripley | Oct 11, 2008 11:20 pm | |
| Dieter Menne | Oct 13, 2008 2:36 am | |
| Prof Brian Ripley | Oct 13, 2008 6:01 am | |
| David Winsemius | Oct 13, 2008 11:59 am |
| Subject: | Re: [R] subsetting dataframe by rownames to be excluded | |
|---|---|---|
| From: | Prof Brian Ripley (rip...@stats.ox.ac.uk) | |
| Date: | Oct 13, 2008 6:01:26 am | |
| List: | org.r-project.r-help | |
On Mon, 13 Oct 2008, Dieter Menne wrote:
Prof Brian Ripley <ripley <at> stats.ox.ac.uk> writes:
Yes: DF[is.na(match(row.names(DF), exclude_me)), ]
Assuming everything is possible in R: would it be possible to make the below work without breaking existing code?
It would be possible, but not I think desirable.
c(exclude) is fine (works now, does nothing useful except strip attributes). But -<char vector> will give an error: that's not necessarily the end, as `[` is a SPECIALSXP and so is passed unevaluated arguments. However, its first step is method dispatch and that evaluates all the arguments, so a substantial internal rewrite would be needed.
It would be fairly easy to make
subset(a, subset=-exclude)
work, and select=-<col_name> already works. I think though that messing with `[` would be too dangerous, and would also lead to expectations that all its methods should accept this notation (and hence many would need to be re-written, including [.data.frame as used here). And then people would expect this to work on RHS, so [<- would need to be re-written ....
a <- data.frame(x=1:10) rownames(a) = letters[1:10] exclude = c("a","c") a[is.na(match(row.names(a), exclude)), ] # not really that easy to remember
a[-c(1,3),] # In analogy.... a[-c(exclude),] #invalid argument to unary operator
Dieter
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-- Brian D. Ripley, rip...@stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
______________________________________________ R-h...@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.